For adjusting a steering wheel position to a sitting position of a driver of a motor vehicle, steering columns are known in various embodiments in the prior art. In addition to a height adjustment by adjusting the tilt of the steering column, the steering wheel mounted to a rear end of the steering spindle in generic steering columns can be positioned in the vehicle interior by a length adjustment in the direction of the steering column longitudinal axis.
The length adjustability is realized by the adjustment unit, which consists of a casing unit and a casing tube, wherein the inner casing tube comprises the rotatably mounted steering spindle, which casing tube is adjustable in the longitudinal direction in the manner of a telescope and is fixable, i.e., releasably securable, in various longitudinal positions by means of a releasable clamping device. The clamping device, also called a securing device, acts on an outer casing unit held on the body, wherein, in the opened state of the clamping device, which is also synonymously called the release position or unclamping position, a displacement of the inner casing tube in the outer casing unit to adjust the steering wheel position is possible and, in the closed state—the fixing position or securing position—the inner casing tube is clamped in the outer casing unit, and the steering wheel position is fixed in normal driving operation under the mechanical loads to be expected.
As an effective measure for improving the safety of occupants in a vehicle collision—the so-called crash event—in which the driver hits the steering wheel at high speed, it is known to design the steering column to be collapsible in the longitudinal direction, even in the fixing position of the clamping device, when a high force which exceeds a limit value that only occurs in the event of a crash is exerted on the steering wheel. In order to ensure a controlled deceleration of a body hitting the steering wheel, an energy absorption device is coupled in between the outer casing unit and the inner casing tube, which are affixed to one another by the clamping device in normal operation, but can be collapsed relative to one another in the event of a crash. This converts the introduced kinetic energy into a plastic deformation of an energy absorption element—for example, by ripping open a tear flap or bending an elongated bending element, such as a bending wire or bending strip.
A generic steering column is described in DE 10 2008 034 807 B3. The clamping device described therein comprises a locking part on the outer casing unit, which locking part can be engaged transversely to the longitudinal direction in a force-fitted and form-fitted manner with a corresponding engagement part on the inner casing tube in the fixing position. In the release position, the locking part is lifted off the engagement part, i.e., released, so that the inner casing tube can be displaced in the longitudinal direction to adjust the steering wheel position.
The engagement part is connected to the inner casing tube by way of an energy absorption device, which is not loaded in normal operation, i.e., forms a rigid connection between the outer casing unit and the inner casing tube. In the event of a crash, however, such a high force is introduced by way of the locking part that the outer casing unit and the inner casing tube move toward each other in the longitudinal direction, wherein the energy absorption element is deformed and the movement is decelerated as a result.
Said DE 10 2008 034 807 B3 furthermore suggests to design the braking effect of the energy absorption device to be controllable in order to, in the event of a crash, take into account whether or not the driver is buckled up, or to be able to adapt to parameters such as the driver's weight, distance to the steering wheel, and the like. In detail, at least two energy absorption elements are, for this purpose, to be provided, which can be activated as needed by coupling them in between the outer casing unit and the inner casing tube, i.e., by their being able to be brought as described above into a mechanical operative connection between the engagement part and the inner casing tube. In doing so, at least a first or a second energy absorption element can be coupled in between the inner casing tube and the engagement part, i.e., either the first or the second or both energy adsorption elements. In this way, an individual braking characteristic adapted to the respective requirement, i.e., a crash degree or crash level, can be realized.
Disadvantageous in the previously known energy absorption device is, however, that the individual energy absorption elements are arranged on respective separate mounting units on opposite sides of the inner casing tube. As a result, a relatively large structural space is taken up, which limits the flexibility in the integration into a vehicle body. On the other hand, the manufacture and separate mounting of at least two energy absorption elements, including the respectively required mounting means, are complex and correspondingly cost-intensive, due to the high number of required components.
Thus a need exists for a steering column with at least two crash degrees, which steering column takes up a smaller amount of structural space and permits an easier and cheaper manufacture.